The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
Burrless drilling systems have been developed by The Boeing Company for performing burrless drilling operations on aircraft fuselage components and other large structures. A burrless drilling system typically includes a pair of flexible tracks that may be secured to an outer surface of a skin panel of a fuselage portion of an aircraft. Typically the tracks are secured by suction cups to the outer surface of the skin panels. The tracks are secured adjacent an area where a splice is to be made, such as where a stringer is positioned to splice two adjacent skin panels together. The flexible tracks support a machining subassembly that may accept, or may have mounted to it, a drill or other machine tool. Also secured to the machining subassembly is an electromagnet that is used to clamp the components being machined together prior to a drilling or other form of machining operation being carried out. The electromagnet, when energized, draws a backing plate positioned on an opposite surface (i.e., the surface that would be inside the fuselage) towards the electromagnet so as to clamp the fuselage components together before the drilling or other form of machining operation begins. Such a system is disclosed in U.S. Pat. No. 7,148,776 and U.S. Pat. No. 6,905,291, both assigned to The Boeing Company. The disclosures of both of these patents are hereby incorporated by reference into the present application.
As will be appreciated, the electromagnet that is carried on the machining subassembly is a relatively heavy item, typically weighing between 30-50 lbs (13.63 kg-22.73 kg). A drill (manual or power feed) is often also carried by the machining subassembly. The drill motor often weighs between 5-10 lbs. (2.27 kg-4.55 kg). When making vertical splices, the user must lift or lower the machining subassembly to a desired position before energizing the electromagnet to clamp the components being machined together. As will be appreciated, this can require considerable effort on the part of an operator. In aircraft fuselage construction applications, typically hundreds of holes need to be drilled along a radial (i.e., vertical) splice line in accordance with a pre-positioned template that is laid over the outer surface of the fuselage skin panel. Thus, over the course of an average work day, repeatedly lifting and/or lowering the machining subassembly to precisely position the subassembly in the needed positions can be physically challenging for the worker.
Initially, just prior to beginning a drilling or machining operation, it would be preferable to be able to enable the user to lower the electromagnet into contact with the outer surface of the skin panel with only a small amount of physical effort being required from the operator. It would also be preferable to enable the electromagnet of the machining subassembly to be lifted away from the skin panel once the drilling operation is completed without the need for significant physical effort from the operator.